1. Field of the Invention
The present invention relates to a method of routing an ATM cell in an ATM network, and more particularly, to a method of routing an ATM cell and a structure of an ATM adaptation layer in an ATM network in which data based on an AAL-Type2 (ATM Adaptation Layer Type2) and an AAL-Type5 (ATM Adaptation Layer Type5) is transferred to the same destination.
2. Discussion of Related Art
In general, the most basic function in a communication network is to select a desired party among a large number of subscribers, connect circuits and freely exchange necessary information.
The ATM switching system among switching systems develops a packet switching principle and simply processes a packet in the midst of a transmission so as to gain a highly speedy operation similar to that in a circuit switching system. The ATM switching system may exchange various information signals having several kinds of natures freely, efficiently, thus this system is very useful for the next generation communication system based on future multimedia information. This ATM switching system can be applied to a desired wired section between a base station and an exchange station, or between the exchange station and a controller.
A protocol stack of individual network elements constructing the ATM network, for example, a base station, an exchange station, etc., is generally composed of an ATM layer, an ATM adaptation layer positioned over the ATM layer, and a user application layer positioned over the ATM adaptation layer. Among them the ATM adaptation layer is classified into an AAL Type1 through an AAL-Type5 according to an object and a characteristic of a user application and a kind of a service class, wherein the AAL-Type2 through the AAL-Type5 are mainly used in a mobile radio communication system.
In the AAL (ATM Adaptation Layer)-Type2, one ATM cell can be multiplexized, therefore can provide a band for the sake of an efficient transmission of a low-rate, short and variable length packet in the user application sensitive to a delay. That is, the AAL-Type2 requires a real time process and is utilized to process sound or image data based on a small quantity of data.
Meantime, the AAL-Type5 improves a service provided by the ATM layer in order to support a function required by its next higher rank layer. The AAL-Type5 performs a function required by a user and a controlling and managing plane, and supplies a mapping between the ATM layer and its next higher rank layer. Thus the AAL-Type5 is used to process connection oriented/connectionless higher rank application user data, e.g., a packet or an IP service, of non-real time and variable length.
The AAL-Type2 and the AAL-Type5 are described referring to the recommendation, I.363.2 and I.363.5 of Telecommunication Standardization Sector of ITU (ITU-T) provided in International Telecommunication Union, as follows.
FIG. 1 represents a protocol stack for the AAL-Type2 based on the ITU-T recommendation. With reference to FIG. 1, the protocol stack of AAL-Type2 based on the ITU-T recommendation is made up of an ATM layer 100, an ATM adaptation layer 200 formed at a higher rank than the ATM layer 100 and subdivided into a common part sublayer (CPS) and a service specific convergence sublayer (SSCS), and a user application layer 300 positioned at a higher rank than the ATM adaptation layer 200. Herewith, AAL-Type2 negotiation procedures (ANP) provides a channel identifier (CID) for individual mini cells which construct one ATM cell.
First, described is in the following a case that data is transferred from the user application layer 300 to the ATM layer 100 through the ATM adaptation layer 200. The data outputted from the user application layer 300 is transferred to the SSCS through an AAL-SAP (Service Access point) 60. The SSCS performs a call linkage operation to the user application layer 300, and transfers the received data to the Common Part Sublayer CPS. The CPS turns the data received from the SSCS into a common part sublayer protocol data unit (CPS-PDU) having a 48 octet type according to a service class as shown in FIG. 1, and transfers it to the ATM layer 100 through an ATM-SAP 13. This CPS-PDU is constructed by a start field 20 containing start information of a field every an ATM cell and by numerous mini cells 30 through 50 which are respectively composed of each of mini cell headers 31,41,51 and each of transmission data 32,42,52. Then, each multiplexized mini cell 30-50 is transferred to a service terminating point desired by a user through one ATM layer connection having one virtual channel identification/virtual path identification value.
Next, operations on the AAL-Type2 are described for a case that the ATM layer 100 receives data in an ATM cell type, as follows. When the ATM layer 100 receives the ATM cell 10, it is transferred to the ATM adaptation layer 200 through the ATM-SAP 13. The CPS analyzes the start field 20 of the received ATM cell 10 and contents of the headers 31,41,51 of each mini cell 30-50, and transfers it to the SSCS. The SSCS each transfers the respective user data 32,42,52 to a corresponding user application layer through the AAL-SAP 60 according to the header 31,41,51 of the mini cell 30-50.
FIG. 2 indicates a protocol stack for the AAL-Type5 based on the ITU-T recommendation. In FIG. 2, the protocol stack of AAL-Type5 based on the ITU-T recommendation is made up of the ATM layer 100, the ATM adaptation layer 200 formed at a higher rank than the ATM layer 100 and subdivided into a convergence sublayer (CS) and a segmentation and reassembly sublayer (SAR), and the user application layer 300 positioned at a higher rank than the ATM adaptation layer 200.
As shown in FIG. 2, one ATM layer is suitable to the structure for servicing one kind of data which mainly means packet data. Therefore, the AAL-Type5 does not have a multiplexing operation for connecting several factors since the mini cells are not used in the inside thereof.
In the following described is a case that data is transferred from the user application layer 300 to the ATM layer 100 through the ATM adaptation layer 200. The data outputted from the user application layer 300 is provided to the CS through the AAL-SAP 60. The CS performs a mapping for the data into a conversions sublayer protocol data unit (CS-PDU) of a 48xn octet type as shown in FIG. 2, and transfers it to the SAR, wherein n is an integer. The SAR subdivides the received data by the 48 octet type, and transfers the subdivided data to the ATM layer 100 through the ATM-SAP 13.
Also, operations for the AAL-Type2 are described as follows, in a case that the ATM layer 100 receives the data in an ATM cell type. When the ATM layer 100 receives the ATM cell 10, the data is transferred to the SAR of the ATM adaptation layer 200 through the ATM-SAP 13. The SAR re-combines the received data by the octet type of 48xn and provides the combined data to the user application layer 300 through the AAL-SAP 60, wherein n represents an integer. Herein, a PAD (Packet Assembly and Disassembly) and trailer 40 provides each of a PAD field and a trailer field, the PAD field indicating an octet presented so that an overall payload becomes a multiple of 48xn in an ending part of a payload 30, the trailer field representing a common part indicator, length and CRC.
However, the ATM adaptation layer of respective elements equipped in such conventional ATM network is provided as only one kind of ATM adaptation layer determined previously in an aspect of a hardware. In other words, each ATM network element is supported in hardware so as to transmit and receive only a characteristic of its own dealing information, an object of a communication, and specific data matched with a service class.
The ATM adaptation layers over two kinds may be, of course, determined in one ATM network element, but in this case, the construction of the ATM network element becomes very complicated in hardware, so such an actual construction is not executed.
Accordingly, data based on the ATM adaptation layers of mutually different types could not be transferred to the same destination at the same time, conventionally. For example, in case data of the AAL-Type2 and the AAL-Type5 types was transferred, all of the data was not processed but only data capable of being processed in a current ATM adaptation layer was processed.
Accordingly, the present invention is directed to a method of routing an ATM cell in an ATM network that substantially obviate one or more of the limitations and disadvantages of the related art.
A primary object of the present invention is to provide a method of routing an ATM cell on an ATM adaptation layer (AAL) in an ATM network in which data based on an AAL-Type2 and an AAL-Type5 can be simultaneously transferred to the same destination by improving the structure of the ATM adaptation layer for individual elements of the ATM network.
Another object of the present invention is to provide the structure of the ATM adaptation layer in an ATM network for supporting a protocol in which an AAL-Type2 and an AAL-Type5 are transferred to the same destination at the same time.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure as illustrated in the written description and claims hereof, as well as the appended drawings.
To achieve these and other advantages, and in accordance with the purpose of the present invention as embodied and broadly described, in a first characteristic, the method of routing an ATM cell on an ATM adaptation layer (AAL) in an ATM network, comprises the steps of: transmitting ATM cells from a plural number of originating party network elements to terminating party network elements through ATM switches according to an ATM adaptation layer type of the originating party network elements, in an ATM network; adding routing information to ATM cell headers on the basis of the ATM cell, on the ATM adaptation layer of the terminating party network element, the routing information being for performing an internal routing of the ATM adaptation layer in the terminating party; and transferring the ATM cell to a corresponding destination on the basis of the routing information of the ATM cell header on the ATM cell adaptation layer of the terminating party network element.
In a second characteristic for achieving another object of the present invention, the structure of the ATM adaptation layer in the ATM network is constructed by an AAL-Type5 sublayer for processing ATM cells of the ATM adaptation layer Type5; and an AAL routing switch controlling layer for adding up AAL routing information for performing a routing to the ATM cell header according to its destination when the received ATM cell passes through the AAL-Type2 or AAL-Type5 sublayer, and switching it to the destination according to the AAL routing information, and these AAL-Type2 sublayer and AAL-Type5 sublayer commonly possess the AAL routing switch controlling layer.
In accordance with such inventive characteristics, the ATM adaptation layer is subdivided into the AAL-Type2 sublayer and the AAL-Type5 sublayer, and the header information for performing the routing is added up in the interior of the ATM adaptation layer in case that an ATM cell to be transmitted passes through the AAL-Type2 sublayer or the AAL-Type5 sublayer. Accordingly, the ATM cell can be transferred to the destination regardless of a type of a transmission ATM cell, e.g., the AAL-Type2 or the AAL-Type5, in one ATM network element based on the present invention.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.